Effect of temperature and pressure on electronic and spectroscopic properties of CdS wurtzoid molecule: A DFT study

Abstract

Temperature and pressure effects on cadmium Sulfide wurtzoid molecule Cd7S7 are investigated using density functional theory. This molecule is of 0.77 nm length. The investigated molecule represents the smallest cluster of atoms from wurtzoids molecules series that shows a hexagonal structure and represents the bulk wurtzite phase as the cluster increases in size. The investigation includes the effect of pressure and temperature on electronic and vibrational properties. The volume change of this molecule is controlled by the bulk modulus and thermal expansion coefficient. Theoretical and experimental results show that both bulk modulus and thermal expansion are more than three times their values at bulk. The results show that increasing the pressure increases the energy gap and Raman longitudinal optical mode due to contraction of the molecule. On the other hand, temperature decreases the energy gap and Raman longitudinal optical mode due to dilation of the molecule. Present results are in good agreement with available experimental results. The electronic orbitals and charges are affected due to pressure and temperature. At high pressure, some electronic charge transforms from S atoms to Cd atoms. At high temperature, the reverse electronic emigration occurs. Orbital occupations change inside each atom itself due to pressure and temperature.